This invention relates to means for controlling the position of an electric drive unit of a control system in response to digital signals indicative of the required change in drive unit position. More specifically, this invention relates to the use of digital signals for regulation of position changes of large drive units which due to high inertia have a non-linear relationship between drive unit travel and time duration of energizing power.
In certain prior art to position the drive unit in response to digital signals, it has usually been necessary to utilize the computer as a means of comparing the actual position of the drive unit with the desired position. That approach is often found undesirable because of the periodic nature of the feedback of a rapidly changing position. In other prior art the drive units have frequently been positioned solely in response to the time duration of the signals sent to the drive units, thus resulting in a non-linear response by failing to take into account the non-linear speed of the drive due to the inertia of the drive unit itself and by a variable load on the drive unit.
It is an object of this invention to provide a means for making precise changes in drive unit positions in a digital control system so as to overcome the disadvantages of the variable relationship between the time duration of energizing the drive unit and its actual change in position.